At the rhythm of language: brain bases of language-related frequency perception in children

What neural mechanisms underlie language and reading acquisition? Slow rhythmic modulations in the linguistic stream (below 8 Hz) mark syllable and word boundaries in the continuous linguistic stream, potentially helping children master the words and structures of their language. Converging evidence across language and reading research suggests that children's sensitivity to these slow rhythmic modulations is important for language and reading acquisition. In infancy, children produce rhythmically alternating syllables, or babbles, at a slow frequency of ~1.5 Hz or 660 ms (Petitto et al., 2001). In early grades, children's sensitivity to slow rhythmic modulations correlates with their reading ability (Goswami, 2011). We used functional Near Infrared (fNIRS) imaging to investigate the brain bases of "language rhythm" in beginning readers (ages 6-9). Right hemisphere showed an overall greater activation toward the slow rhythmic stimuli, and left hemisphere showed greater activation toward 1.5 Hz, relative to faster and slower frequencies. The findings suggest that while right hemisphere might have an overall better ability to process rhythmic sensitivity, left hemisphere might have a select sensitivity to a preferred range of slow rhythmic modulations-a range that might be particularly salient to brain mechanisms responsible for cross-modal language processing and reading acquisition.